Melanocytes are essential to protecting the skin from the harmful effects of UV radiation. Paradoxically, melanocytes are the precursors of the most deadly form of skin cancer, melanoma. Melanoma is one of the fastest growing tumor types in the United States and the number of cases worldwide has doubled in the past 20 years. Melanoma is an extremely aggressive tumor and incredibly resistant to current therapies. If melanoma is detected early, before the tumor becomes invasive, it can be cured through surgical resection. Unfortunately, melanoma lesions can remain unidentifiable or asymptomatic for long periods of time. Therefore, the identification of informative biomarkers and molecular targets for the chemoprevention of melanoma progression is vital to the control of this deadly disease. This proposal builds on the novel observation that three UGTs (UGT2B7, UGT2B10 and UGT2B15) are normally expressed in human melanocytes and that their expression is lost during melanoma progression. Since the UGTs are a vital part of the cells natural defense mechanisms against cancer formation, we hypothesize that loss of UGT expression is required for melanoma progression. This proposal is focused on elucidating if and when UGTs are lost during melanoma progression in using human tissues and how that loss may cause melanocytes to become melanoma. Evidence presented here show that UV radiation, which has long been implicated in a causal role for melanoma, downregulates UGT expression in melanocytes. This observation will be further characterized to elucidate if both UV-A and UV-B triggers reduction of UGT expression and if that reduction correlates to a loss of overall UGT activity. This proposal will also investigate the role of UGT activity in melanoma progression. Since UGT2B7, UGT2B10 and UGT2B15 all can inactivate the bioactive lipid 12-hydroxyeicosatetraenoic acid (12-HETE) and elevated 12-HETE levels have been correlated to melanoma progression, we hypothesize that human melanoma is driven by uncontrolled 12-HETE signaling through loss of UGT expression. To test this, UGT2B7, UGT2B10 and UGT2B15 will be stably overexpressed in metastatic melanoma cells and the levels of 12-HETE will be monitored and correlated with alterations in cell proliferation, apoptosis and invasiveness Conversely, shRNA will be used to knockdown UGT expression in primary melanoma cells to see if those cells progress to more aggressive melanoma stages by examining their growth, ability to avoid apoptosis and increased invasiveness. These results will also be correlated to 12-HETE and 12-HETE-glucuronide levels. Results from the studies proposed here will enhance our understanding of melanoma progression and identify new informative biomarkers as well as novel targets for therapeutic intervention of this deadly disease.